Geoscience Reference
In-Depth Information
activities and as a vital protein source, puts us in a
vulnerable situation. Disrupting the oceanic system
could have potentially catastrophic consequences
for humankind. Risks to economic and societal wel-
fare include disturbances to seafood resources and
the deterioration of coral reefs, both of which could
lead to losses to the i shing and tourism industry,
decreased biodiversity, and threatened food security
for populations relying to a large extent on seafood
as a protein source (Cooley
et al.
2009 ; Kleypas and
Yates 2009). At a US Senate hearing in April 2010,
representatives of the tourism, i shing, and diving
industries testii ed to their concern about the impact
of ocean acidii cation on their activities. Two gen-
eral examples of socio-economic risks associated
with ocean acidii cation are briel y introduced
below. The reader is referred to Chapter 13 for a
thorough analysis.
was estimated at US$91.2 billion in 2006 (FAO 2009),
indicating the potentially large economic conse-
quences of decreased seafood harvests.
Fisheries and seafood industries represent both
commercial and recreational interests, that contribute
an economic value via travel and purchases of per-
mits and equipment. Furthermore, numerous jobs
depend on i shery industries, from i shermen to afi li-
ated industries such as processing, transportation,
preparation, and sales (Cooley and Doney 2009a).
Disturbances to trophic dynamics may pose an
indirect threat to i sheries. For example, shelled pter-
opods play a key role in some marine food webs and
their decline or disappearance might cause perturba-
tions in trophic levels important to humans. The con-
sequences of changing food web structure are
potentially dire. Even if the direct effect of an unbal-
anced food web is difi cult to estimate, it is clear that
the future success of top predators will depend on
their capacity to alter their food sources and whether
alternative prey will be available (i.e. species that are
resistant to or unaffected by ocean acidii cation and
have the nutritional qualities required to function as
a substitute; Cooley and Doney 2009a).
1.5.1.1 Commercial seafood species and i sheries
The potential threat of ocean acidii cation to the sea-
food industry is twofold and can be expressed in
terms of: (1) direct impacts on commercially valua-
ble species, and (2) indirect effects via perturbations
to the marine food web. The most studied direct
effect on seafood is associated with the process of
calcii cation. It has been shown that many calcare-
ous organisms will have problems forming their
shells or skeletons in an ocean rich in CO
2
. For exam-
ple, laboratory experiments on calcifying species of
shelli sh with a commercial value, such as the blue
mussel,
Mytilus edulis
, and the Pacii c oyster,
Crassostrea gigas
, have shown a decrease in calcii ca-
tion of 25 and 10%, respectively, for conditions of
ocean chemistry projected for the end of the 21st
century (Gazeau
et al.
2007 ). However, the extrapola-
tion of laboratory results to the natural environment
is difi cult, and some species are unaffected (Miller
et al.
2009). The effects of ocean acidii cation on mol-
luscs therefore remain unknown, despite the fact
that the aquaculture industry represents a billion
dollar industry worldwide and food security for
millions of people. In addition to consequences for
the ability of species to calcify their shell or skeleton,
ocean acidii cation may have direct (effects on
metabolism or reproduction) and indirect (prey or
habitat loss) negative impacts on economically
important i ni sh (Cooley and Doney 2009a). The
i rst-sale value of the global i sheries production
1.5.1.2 Coral reefs
Coral reefs are among the ecosystems most sensi-
tive to the combined effects of elevated
p
CO
2
and
temperature (Hoegh-Guldberg
et al.
2007 ; Cooley
and Doney 2009a ; see also Chapter 15 ). Several
studies have shown that coral reef ecosystems might
shift from a state of calcium carbonate construction
to erosion under the pressure of ocean acidii cation
(e.g. Silverman
et al.
2009). Their damage or loss
could have direct and indirect detrimental conse-
quences, including impacts on commercially or eco-
logically important i shes that feed and reproduce
in reefs, on the particularly rich biodiversity inhab-
iting the reefs, and on the tourism industry and pro-
tein supply for millions of people, most of whom
live in the poorest areas of the world (Donner and
Potere 2007 ; Kleypas and Yates 2009 ). Coral reefs
also protect other important biodiversity-rich eco-
systems such as mangroves and seagrass beds, and
play a key role in protecting shorelines from erosion
and inundation. Cesar
et al.
( 2003 ) estimated the
potential net benei t from coral reefs (taking into
account i sheries, coastal protection, tourism, and
biodiversity value) at US$30 billion yr
-1
.
